CHAPTER XIV 
PHYLUM VIII. BRYOPHYTA 
THE MOSSWORTS 
418. This phylum includes plants of much greater 
complexity than any of the preceding. In yery many 
cases they have distinct stems and leaves, whose tissues 
often show a differentiation into several varieties. In 
the sexual organs the cell to be fertilized (the egg) is from 
the first enclosed in a protective layer of cells, and after 
fertilization it develops into a complex spore-bearing 
body. 
419. The life-cycle of the Mossworts includes a dis- 
tinct alternation of generations. The immediate prod- 
uct of the fertilization of an egg is not a thalloid or leafy 
plant like that which bears the sexual organs, but, on the 
contrary, it is a many-celled leafless structure, spherical 
or approximately cylindrical, which eventually produces 
spores internally. The plant which produces the sexual 
organs is the gametophyte, while that which produces the 
spores is the sporophyte. 
420. So the Mossworts have a marked duality, and we 
must consider both phases when we wish to get a complete 
idea of any particular plant. This duality has permitted 
the acquisition of the land habit, since the gametophytes 
have retained some of their aquatic characteristics, while 
the sporophytes have become modified for a terrestrial 
life. Accordingly in Bryophytes we find the beginning of 
the terrestrial habit in green plants. 
242 
